namespace SnippingTool;

public partial class SnippingTool : Form
{
	public static Image? Snip()
	{
		var rc = Screen.PrimaryScreen.Bounds;
		using Bitmap bmp = new Bitmap(rc.Width, rc.Height, System.Drawing.Imaging.PixelFormat.Format32bppPArgb);
		using Graphics gr = Graphics.FromImage(bmp);
		gr.CopyFromScreen(0, 0, 0, 0, bmp.Size);
		using var snipper = new SnippingTool(bmp);

		return snipper.ShowDialog() == DialogResult.OK ? snipper.Image : null;
	}

	public SnippingTool(Image screenShot)
	{
		InitializeComponent();
		BackgroundImage = screenShot;
		ShowInTaskbar = false;
		FormBorderStyle = FormBorderStyle.None;
		WindowState = FormWindowState.Maximized;
		DoubleBuffered = true;
	}
	public Image? Image { get; set; }

	private Rectangle rcSelect = new Rectangle();
	private Point pntStart;

	protected override void OnMouseDown(MouseEventArgs e)
	{
		if (e.Button != MouseButtons.Left)
		{
			return;
		}
		pntStart = e.Location;
		rcSelect = new Rectangle(e.Location, new Size(0, 0));
		Invalidate();
	}
	protected override void OnMouseMove(MouseEventArgs e)
	{
		if (e.Button != MouseButtons.Left)
		{
			return;
		}
		int x1 = Math.Min(e.X, pntStart.X);
		int y1 = Math.Min(e.Y, pntStart.Y);
		int x2 = Math.Max(e.X, pntStart.X);
		int y2 = Math.Max(e.Y, pntStart.Y);
		rcSelect = new Rectangle(x1, y1, x2 - x1, y2 - y1);
		Invalidate();
	}
	protected override void OnMouseUp(MouseEventArgs e)
	{
		if (rcSelect.Width <= 0 || rcSelect.Height <= 0)
		{
			return;
		}
		Image = new Bitmap(rcSelect.Width, rcSelect.Height);
		using Graphics gr = Graphics.FromImage(Image);
		gr.DrawImage(BackgroundImage, new Rectangle(0, 0, Image.Width, Image.Height),
			rcSelect, GraphicsUnit.Pixel);
		DialogResult = DialogResult.OK;
	}
	protected override void OnPaint(PaintEventArgs e)
	{
		using Brush br = new SolidBrush(Color.FromArgb(120, Color.White));
		int x1 = rcSelect.X; int x2 = rcSelect.X + rcSelect.Width;
		int y1 = rcSelect.Y; int y2 = rcSelect.Y + rcSelect.Height;
		e.Graphics.FillRectangle(br, new Rectangle(0, 0, x1, Height));
		e.Graphics.FillRectangle(br, new Rectangle(x2, 0, Width - x2, Height));
		e.Graphics.FillRectangle(br, new Rectangle(x1, 0, x2 - x1, y1));
		e.Graphics.FillRectangle(br, new Rectangle(x1, y2, x2 - x1, Height - y2));

		using Pen pen = new Pen(Color.Red, 3);
		e.Graphics.DrawRectangle(pen, rcSelect);
	}
	protected override bool ProcessCmdKey(ref Message msg, Keys keyData)
	{
		if (keyData == Keys.Escape)
		{
			DialogResult = DialogResult.Cancel;
		}
		return base.ProcessCmdKey(ref msg, keyData);
	}
}